wil6210: Introduce struct for sw context

Enable adding more data to the SW context.
For now, add flag "mapped_as_page", to separate decisions on free-ing skb
and type of DMA mapping.
This allows linking skb itself to any descriptor of fragmented skb.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Git-commit: f88f113a54f02df62608ec263e8a3ff7e81cfce2
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Liron Kuch <lkuch@codeaurora.org>